Detectors of the type under consideration may detect incoming noise or other signals by using diode detector circuits. In such a detector, one or more diodes may be used in a rectifier circuit whose complexity may vary considerably, depending on the application and the specific requirements.
Irrespective of the type of diode detector circuit used, most such circuits have at least two drawbacks: a lack of gain and a diode offset voltage. The latter problem arises from the fact that a diode includes an inherent offset voltage which must be overcome by the incoming signal before useful detection can occur. Consequently, very small signals are difficult to detect in this manner.
Another problem with diode detectors resides in their inherent temperature dependence. As ambient temperature varies, the detected output of the diode can vary consideraly. In many applications such temperature dependent operation is not acceptable.